PB2139: A REAL-WORLD OUTCOME OF NEWLY DIAGNOSED PRIMARY MEDIASTINAL B-CELL LYMPHOMA TREATED WITH 6 CYCLES OF R-CHOEP-14 AND 2 CYCLES OF DHAP FOLLOWED BY AN AUTOLOGOUS STEM CELL TRANSPLANT
Authors: J. Tan Tsen Chuen, K. W. Ho, P. L. Low, L. C. Chow, G. Kasinathan, C. Ng, S. Shahnaz Alkudsi, S. M. Tan
Journal: HemaSphere (2022)

Background: Historically, Primary Mediastinal B-Cell Lymphoma (PMBL) treated at our centre with 6 cycles of R-CHOP-21 appears to have a poorer outcome compared to the conventional DLBCL. There were few prospective randomized studies to look specifically at the optimal treatment of PMBL. Some physicians advocated more intensified regimens such as R-DA-EPOCH, R-HYPERCVAD, VACOP-B/MACOP-B or the BFM ALL protocol. A prospective phase 2 study by Dunleavy et al. in 2013 showed an impressive outcome with R-DA-EPOCH and had become the preferred regimen at our centre. However in real-world practice, adhering to this intensified regimen was difficult and doses were rarely escalated beyond level 2. Logistic problems at our centre with arranging central venous access, monitoring counts and timely admissions result in delays in administration. Aims: To evaluate the efficacy and tolerability of 6 cycles of R-CHOEP-14 followed by 2 cycles of DHAP and an autologous stem cell transplant. Methods: At the treating physician’s discretion, PMBL patients diagnosed between August 2019 - Sept 2021 were offered 6 cycles of R-CHOEP-14 followed by 2 cycles of DHAP and an autologous stem cell transplant with standard BEAM conditioning. Etoposide was given orally whenever possible and prophylactic GCSF was given routinely. The primary treatment was done in an outpatient setting whenever possible. Patients also received consolidation radiotherapy to the mediastinum at the physician’s discretion. Results: At data cut off, a total of 16 patients have completed their treatment. 87.5% (14) of patients were male, and 12.5% (2) of patients were female. Median age was 33.5 years (25-42). All patients had bulky disease > 7cm, B symptoms and Stage ≥2. 93.8% (15) had elevated serum LDH. One patient received 2 cycles of high dose methotrexate & cytarabine instead of DHAP as he was deemed at high risk of CNS relapse. 37.5% (6) of patients also received radiotherapy at the treating physician’s discretion either prior to or after transplant. The mean duration between the R-CHOEP cycles were 18 days, with a median of 16 days and mode of 14 days. 37.5% (6) of patients had a PET/CT done either prior or after the transplant and among these, 83.3% (5) achieved a complete metabolic remission. With a median follow up of 48 weeks (12-129), progression free survival (PFS) was 100% and the overall survival (OS) was 93.8%. There was one unexpected treatment related mortality (TRM) due to massive pulmonary haemorrhage which may be related to patient’s pulmonary stent removal prior to his 6th R-CHOEP chemotherapy. Serious adverse events were rare, one patient developed CMV retinitis which resolved upon treatment. No patient had progressed or relapsed. Image:Summary/Conclusion: 6 cycles of R-CHOEP-14 followed by 2 cycles of DHAP and an autologous stem cell transplant is feasible and well tolerated with limited toxicity. The primary regimen can be done in an outpatient setting, does not require central venous access, easier to adhere to and can be completed within a shorter time frame. The early PFS and OS appears comparable to historical real-world outcome of intensified regimens such as R-DA-EPOCH. Longer follow up will be desirable to evaluate long term outcome and toxicity.